Abstract: The dynamic variation of groundwater level is the most intuitive factor for measuring whether the groundwater system is in a benign cycle. The shallow groundwater in over-exploitation areas of Anyang plain is taken as the research object. This paper comprehensively considers multiple constraints including soil salinization, vegetation ecological security, underground structures and aquifer thickness to determine the controlled critical groundwater level. The percentile statistical method is used for water level early warning based on the impact of South-to-North Water Diversion Project. The coupling mechanism between the critical water level and early warning of groundwater is studied. The results show that the upper limit water level of shallow groundwater is 48.09-128.20 m, and the lower limit water level is 18.55-49.35 m. The red early warning areas of groundwater show significant spatial agglomeration characteristics, mainly distributed in Neihuang County and Anyang County. After the water supply of the South-to-North Water Diversion Project, only the blue early warning water level in parts of urban Anyang exceeds the upper limit water level. The red early warning water level in Neihuang County is lower than the lower limit water level, and the early warning water levels of other counties are all within the range between the upper and lower limit water levels.

Key words: critical water level of groundwater, early warning of groundwater, percentile statistics method, shallow overexploitation area